Condensed Fonts and Skeletons

Just a question on how condensed fonts work, if I'm creating a typeface based off the skeleton of a regular font but wanted to created a condensed version of it I would expand the stroke of the type inwards rather than balancing it on both ends of the skeleton correct? In other words unlike a bold version of the regular or roman font where the expanded stroke would rather evenly from right to left comes from the skeleton it would instead only expand inwards.

Image included with black being the roman, yellow is bold condensed, and magenta is bold. The typeface for this example is set in Univers while the typeface I'm using as my skeleton is Forza, I choose Univers simply because Forza does not at this time have a condensed font.

I'm aware that by doing the work in the image it sort of answers the question but I was wondering if this is how it is always done for creating condensed, or should I just go on and looking other typefaces to see if they carry the same traits.

While a condensed ultralight might be straightforward, a condensed black will probably require a redesign of several glyphs. Look at some classic sans serif families with condensed and compressed styles and see how they treat the rounds (ODCG etc). They're often a bit more square than the regular width glyphs. I'm not sure why . . . I think it just looks better. That squareness changes the relationship those rounds have with other letters. The M & W are tricky to squeeze into a condensed black and can cause other letters to look too narrow. Does your font look okay with a really wide M & W? That will affect the design of the rest of the letters. How skinny of a T can you get away with next to that wide M?

Figure out which letters are critical to the condensed design and work those out. Let's say you decided to use ABKMOSWow. Create a condensed black version of those letters, complete with proper spacing. Test alongside to the original width font to make sure you haven't lost the essence of the original. Once you're happy with you new narrow letters, you can use them to extrapolate the rest of the font. Constantly compare to the regular width font so you can keep it consistent.

The widths of those test letters can be used to calculate the widths of the rest of the alphabet. If your next letter is an H, type HAHBHKHMHOHSHWHoHwH and adjust the width until the H seems to harmonize with the other letters.